The success of a knee replacement procedure may be dependent at least in part upon the integrity of the anterior cruciate ligament (“ACL”) of the patient. For example, unicondylar knee replacement (“UKR”) and bi-cruciate retaining knee replacement (“BCR”) procedures replace one or more articular surfaces of the knee joint while preserving the ACL. Thus, the constraint provided by the ACL affects the outcome of UKR and BCR procedures, as opposed to knee replacement procedures which sacrifice the ACL.
Physicians may use qualitative tests to determine whether a patient's ACL has ruptured. One such test is an anterior drawer test of the knee. In an anterior drawer test, a patient lies supine with the hips flexed 45° and the injured knee flexed 90°. The physician grasps the lower leg near the knee joint and translates the leg anteriorly. The procedure is performed on both legs, and if the anterior tibial translation of the injured knee is greater than that of the uninjured knee, the physician may diagnose the patient with a ruptured ACL.
Although qualitative ACL integrity tests may provide useful information, such tests are generally binary in that the ACL is diagnosed as intact or ruptured without the ability to reliably diagnose injured but intact ACL conditions. Such tests may also lack reliability. For example, if an anterior drawer test is performed on a patient while the patient's hamstring muscles are contracted, a false negative may result despite the ACL being ruptured. Thus, it would be preferable to have the ability to perform a diagnostic that reliably diagnoses ACL deficiency and is capable of determining the type of deficiency as well as provide quantitative information regarding the integrity of the ACL.